1. Field of the Invention
This invention relates to methods of automatic control in plasma processing and more particularly to process control of plasma manufacturing with a computer control system for manufacture of products such as integrated circuit semiconductor devices.
2. Description of Related Art
Plasma processing technologies which are practiced in plasma chambers have been widely used in IC (Integrated Circuit) manufacturing processes. For example, plasma etching, Chemical Vapor Deposition (CVD), and sputtering processes have been used.
U.S. Pat. No. 5,347,460 of Gifford et al. for "Method and System Employing Optical Emission Spectroscopy for Monitoring and Controlling Semiconductor Fabrication" shows a method and system employing Optical Emission Spectroscopy (OES) for monitoring and controlling flow rates of gases in a semiconductor fabrication process; generally discussing on-line controlling plasma processes by OES using very specific control rules as well as general control rule principles.
U.S. Pat. No. 5,661,669 of Mozumder et al. shows a "Method for Controlling Semiconductor Wafer Processing" that relates to a process control system which includes use of an in situ optical sensor such as a monochromator for measuring process parameters during semiconductor wafer fabrication/processing. For example, the monochromator can generate a signal proportional to the concentration of a predetermined chemical species in a processing unit. The system is adapted to be used for run-to-run control of semiconductor wafer processing by comparing a measured quality characteristic with an expected quality characteristic.
U.S. Pat. No. 5,546,322 of Gifford et al. for "Method and System for Analyzing Plasma Data" shows control rules and a system for analyzing plasma data. Analysis of plasma data indicative of gaseous species therein, such as Optical Emission Spectroscopy (OES) data, is aided through the interactive use of a computer.
U.S. Pat. No. 4,242,188 of Niinomi et al. for "Method for Controlling Plasma Chemical Reactions" shows a method for controlling plasma chemical reactions by plasma constants. The plasma constants in the progress of reaction such as electron temperature, electron density and electron energy distribution function can be measured by use of a probe heated to a high temperature which is made of a metal having a small thermionic electron emission at a high temperature. The plasma chemical reaction can be performed in the steady state with satisfactory reproduction of composition, structure, yield and performance of the product by controlling the pressure, input power and gas flow rate in the plasma reactor so that the measured plasma constants always coincide with the predetermined plasma constants necessary for effecting the intended chemical reaction which have been obtained through a preliminary experiment.